Final answer:
The process in which macrophages secrete cytokines inducing changes in the vascular endothelium, thereby facilitating the migration of neutrophils into the tissue, is called transendothelial migration.
Step-by-step explanation:
The process described, where macrophages secrete cytokines leading to changes in the vascular endothelium that allow neutrophils to migrate into infected or inflamed tissues, is known as transendothelial migration.
This is a critical part of the inflammatory response, which involves the dilation of capillaries and increased permeability of the capillary walls. As a result, blood flow to the affected area increases and leukocytes, including neutrophils and monocytes that differentiate into macrophages, are able to migrate from the bloodstream into the tissue spaces to attack pathogens and initiate tissue repair.
During this immune response, neutrophils are among the first leukocytes to arrive, releasing chemicals that can destroy pathogens and also carrying out phagocytosis to engulf and digest the invading organisms. This sequence of events is pivotal in protecting the body against infection and facilitating the healing process.